If two people are cohabiting, they are living together and have a sexual relationship, but are not married.
例句
In Italy people hardly ever cohabit...在意大利，很少有人未婚同居。The dentist left his wife of 15 years and openly cohabited with his receptionist...那個牙醫(yī)離開了和他生活了15年的妻子，與自己診所的接待小姐公開同居。
英漢詞典釋義
vi.
(未婚者)同居
Ann had been cohabiting with Jim for years before getting married.安在結(jié)婚前曾和吉姆同居了好幾年。
英英詞典釋義
Verb
1. room or live together; usually said of people who are not married and live together as a couple